U.S. nuclear sub runs aground in Pacific

20 crew members injured

(CNN) -- U.S. Coast Guard and military aircraft Saturday are en route to the western Pacific, where a nuclear attack submarine ran aground, injuring at least 20crew members -- one critically, U.S. Navy sources said.

The USS San Francisco ran aground some 350 miles south of Guam -- the nearest land mass -- while it was conducting submerged operations. It has since resurfaced and is heading back to Guam, according to the USPF's news release.

"At this point there does not seem to be damage to the (nuclear) reactor," Lt. Adam Clampitt told CNN, from his base in Pearl Harbor, Hawaii.

There are 137 crew members on board the USS San Francisco. In addition to the one critically injured crew member, 19 others were injured to the extent that they are unable to work, the sources said.

Most of the wounded suffered head injuries, Clampitt said.

"Our first concern is the safety of the crew," Clampitt said.

The Navy sources said the military hopes to evacuate the injured.

The nuclear-powered vessel is a Los Angeles-class "fast attack" submarine. Clampitt said it was carrying four torpedo-tubes, which can launch Tomahawk cruise missiles. It is the most common type of U.S. attack submarine in the fleet.